1. Technical Field
This invention relates generally to fluidized support beds, and more particularly, to an air support bed that utilizes fluidized pellets in a mattress to support a body on the bed.
2. Background Art
Beds that utilize a confined quantity of a medium of fluidized pellets in the form or silica beads, or media, to support ulcerated or burned bodies of hospital bed-ridden patients are well known in the art. Basically a mattress in the form of a generally rectangular bag has fluid impervious walls and bottom and a fine mesh or membrane support surface on which the patient lies. The bag is filled with a plurality of pellets or beads that are suspended by air pressure in the bag, which is usually supplied by a blower through a port in the bag bottom. Examples of this are shown in U.S. Pat. No. 3,428,973—Hargest et al. One problem with such a fluidized bed is that the weight distribution of the patient creates an unequal fluid flow and, hence, pressure distribution across the entire bed. The position of the patient's body on the mattress varies the supporting pressure throughout the mattress, which causes unequal support of various portions of the patient's anatomy.
One method of equalizing pressure across the support surface is to make the pore size of the membrane exceedingly small, to more nearly equalize the flow rate by using a much higher pressure throughout the mattress. This results in the need to utilize a powerful blower which increases the cost. Other attempts to equalize the pressure distribution across the entire bed are disclosed in U.S. Pat. No. 4,637,083—Goodwin, U.S. Pat. No. 4,425,676—Crane, and U.S. Pat. No. 4,599,785—Tominaga, which all attempt to compartmentalize the mattress and isolate each compartment. This isolation attempts to equalize the pressure for all compartments and equally support all body portions with equal pressure. None of the structures in these patents truly creates an equal pressure distribution across the mattress and resultant equal support for all portions of the patient's body. A comprehensive summarization of the prior art patents which address the problems involved in providing a hospital patient support bed can be found in Published U.S. Application US 2005/0060809, published Mar. 24, 2005, section entitled “DESCRIPTION OF PRIOR ART” which is incorporated herein by reference. All presently known designs fail to provide equal support for all portions of a body that is placed on the mattress, regardless of the orientation and location of the body on the mattress.
It would be desirable to provide a fluidized bed that provides equal support for all portions of a body that is placed on the mattress, regardless of the orientation and location of the body on the mattress.